Let’s look at this text in isolation.
This is negative (did not convince), ambiguous (it sounds like you dismissed Elliot’s reasoning, but you might not have), and undermining.
Undermining basically involves negativity plus indirectness. Undermining can also involve attacking something’s foundations and doing gradual damage over time.
How is it indirect? You didn’t give arguments for Elliot to respond to. You didn’t engage in debate. You didn’t directly, openly say what the issues/criticisms are, which would let readers judge for themselves about each point. You suggested his arguments aren’t good enough without being specific. It’s indirect because, instead of (directly) stating your criticisms, you talked about them without sharing what they were. There’s no good way to defend against or counter that kind of negativity.
Negativity that is expressed directly can be responded to directly. Indirect negativity is problematic because if you respond in an indirect way it’s not a good defense. E.g. if you say “you didn’t give arguments, so you should be presumed wrong and ignored” that doesn’t counter the unstated criticisms and actually gives the person more attention. And it’s often messy because the person did give some arguments about something, just not direct responses to the article text. And people often will respond to a direct defense by denying they were even attacking the article (while continuing to hint that they are).